Cross member for a motor vehicle sub-frame

ABSTRACT

A cross member for a motor vehicle sub-frame includes (a) a hollow body having an extrusion axis and (b) a wall having a first edge and a second edge. The wall is positioned inside and extends across the hollow body with the first edge and the second edge joined to the hollow body.

This application is a divisional of U.S. patent application Ser. No.14/989,454 filed on 6 Jan. 2016, the full disclosure of which isincorporated herein by reference.

TECHNICAL FIELD

This document relates generally to the motor vehicle equipment fieldand, more particularly, to an extruded multi-component motor vehiclesub-frame as well as to an extruded side rail and extruded cross-memberfor that sub-frame.

BACKGROUND

The use of aluminum by the automotive industry could achieve over 30%weight savings in vehicle body, chassis and closure components whenreplacing steel parts. An aluminum intensive vehicle is an efficient wayto reduce weight and thus improve fuel economy.

The sub-frame or engine cradle is an assembly with high potential forweight saving due to its size and weight. Conventional sub-frames aremade of stamped steel parts. Some high performance automobiles utilizealuminum sub-frames made of aluminum castings or combinations ofaluminum castings and extrusions. An aluminum sub-frame made by onlyextrusions is more attractive to automotive manufacturers sinceextrusion dies are more affordable compared to casting dies.

It is challenging to design a perimeter type sub-frame with onlyextrusions to achieve stiffness, performance and weight savings due tothe architecture of the sub-frame and the manufacturing constraints ofextrusions. More specifically, a perimeter type sub-frame is constructedwith a front cross member, a rear cross member and two side rails. Themost efficient stiffness design of the side rail should have a closedcross section or partially closed sections at critical locations thatwill benefit both bending and torsion resistances. Unfortunately, thepackage space of a sub-frame generally will not allow a straight siderail with a sufficient cross section size, thereby limiting the use ofextruded tubes. Thus, in the past, package feasible side rail componentshave been made by either lateral direction or vertical directionextrusions which have two open surfaces.

This document relates to a new and improved motor vehicle sub-frame, aside rail for that sub-frame and a cross member for that sub-frame.Design challenges are overcome by providing an all extruded aluminumperimeter sub-frame that meets or exceeds strength, bending resistanceand torsion resistance requirements while providing substantial weightsavings for increased fuel economy. Thus, the motor vehicle sub-framedisclosed herein represents a significant advance in the art.

SUMMARY

In accordance with the purposes and benefits described herein, a motorvehicle sub-frame is provided. That motor vehicle sub-frame comprises afront cross member, a rear cross member, a first side rail connectingthe front cross member with the rear cross member at a first side of themotor vehicle sub-frame and a second side rail connecting the frontcross member with the rear cross member at a second side of the motorvehicle sub-frame. The first and second side rails both include a firstcomponent having a first extrusion axis and a second component having asecond extrusion axis. The first component is joined to the secondcomponent with the first extrusion axis and the second extrusion axisforming an included angle of between 60° and 90°.

In one possible embodiment, the first component includes a first partand a second part wherein a first end of the first part is joined to asecond end of the second part. In one possible embodiment, the secondcomponent includes a first element and a second element. The firstelement is joined to the inner surface of the first part and the secondelement is joined to the inner surface of the second part. Thus, thefirst component may include a first wall, forming an upper wall of theside rail and a second wall, forming a lower wall of the side rail.Further, the second component includes a third wall, forming an innerside wall of the side rail and a fourth wall, forming an outer side wallof the side rail. Accordingly, the second component may be positioned inthe first component and the third wall and the fourth wall may be joinedto the inner surfaces of the first wall and the second wall. In this wayit is possible to produce at least a partially closed side rail from twoextruded components.

In accordance with an additional aspect, a motor vehicle sub-frame isprovided including a front cross member, a rear cross member and firstand second side rails connecting the front and rear cross members atrespective first and second sides of the motor vehicle sub-frame. Thefirst side rail and the second side rail are joined to the rear crossmember by one or more friction stir welds while the first side rail andthe second side rail are joined to the front cross member by one or moreMIG welds.

The motor vehicle sub-frame further includes a first front bodyattachment and a second front body attachment. The first front bodyattachment is joined to the first side rail by a first MIG weld and thesecond front body attachment is joined to the second side rail by asecond MIG weld.

In accordance with still another aspect, a side rail is provided for amotor vehicle sub-frame. That side rail comprises a first componenthaving a first extrusion axis and a second component having a secondextrusion axis. The first component is joined to the second componentwith the first extrusion axis and second extrusion axis forming anincluded angle of between 60 and 90 degrees.

More specifically, the first component includes a first wall, forming anupper wall of the side rail, and a second wall, forming a lower wall ofthe side rail. The second component includes a third wall, forming aninner side wall of the side rail, and a fourth wall, forming an outerside wall of the side rail.

In one possible embodiment, the second component is positioned in thefirst component and the third wall and fourth wall are joined to theinner surfaces of the first wall and the second wall.

In another possible embodiment, the first component includes a firstpart and a second part wherein a first end of the first part is joinedto a second end of the second part. In such an embodiment, the secondcomponent may include a first element and a second element. The firstelement is joined to an inner surface of the first part while the secondelement is joined to an inner surface of the second part. Thus, thesecond component at least partially closes the first component toprovide and at least partially close the side rails. The first andsecond components may be joined by a weld.

In accordance with still another aspect, a cross member is provided fora motor vehicle sub-frame. That cross member comprises a hollow bodyhaving an extrusion axis and a wall having a first edge and a secondedge. The wall is positioned inside and extends across the hollow bodywith the first edge and the second edge joined to the hollow body.

In one possible embodiment the wall has a longitudinal axis that extendsparallel to the extrusion axis of the hollow body. Further the wall maybe planar.

The hollow body may include an attachment hole and the wall is alignedwith that attachment hole. Still further, a cylindrical reinforcementmay be provided in the hollow body around the attachment hole. In suchan embodiment, the wall may extend radially outwardly from thecylindrical reinforcement but the wall does not cross the attachmenthole defined within the cylindrical reinforcement. Thus, the wallextending across the hollow body is discontinuous.

In the following description, there are shown and described severalpreferred embodiments of the motor vehicle sub-frame, the side rail fora motor vehicle sub-frame and the cross member for the motor vehiclesub-frame. As it should be realized, the motor vehicle sub-frame, siderail and cross member are all capable of other, different embodimentsand their several details are capable of modification in various,obvious aspects all without departing from the sub-frame, side rail andcross member as set forth and described in the following claims.Accordingly, the drawings and descriptions should be regarded asillustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The accompanying drawing figures incorporated herein and forming a partof the specification, illustrate several aspects of the motor vehiclesub-frame, the side rail for a motor vehicle sub-frame and the crossmember for a motor vehicle sub-frame and together with the descriptionserve to explain certain principles thereof. In the drawing figures:

FIG. 1 is a perspective view of a first possible embodiment of the motorvehicle sub-frame.

FIG. 2A is a perspective view of a first component of a side railincluding first and second parts that are joined end to end.

FIGS. 2B and 2C are perspective views illustrating first and secondelements of a second component for a side rail of a motor vehiclesub-frame.

FIG. 2D is a perspective view illustrating the assembled side railutilizing the components illustrated in FIGS. 2A-2C.

FIG. 3 is a perspective view of the rear cross member of the motorvehicle sub-frame.

FIG. 4 is a detailed perspective view of that rear cross memberillustrating the structural details of the cross member including thehollow body including various attachment holes, the cylindricalreinforcements for those attachment holes and the reinforcing walls,aligned with the cylindrical reinforcements and attachment holes,extending across the hollow body.

Reference will now be made in detail to the present preferredembodiments of the motor vehicle sub-frame, the sub-frame side rail andthe sub-frame cross member, examples of which are illustrated in theaccompanying drawing figures.

DETAILED DESCRIPTION

Reference is now made to FIG. 1 illustrating a motor vehicle perimetersub-frame or engine cradle 10. As illustrated, the sub-frame 10 includesa front cross member 12, a rear cross member 14, a first side rail 16and a second side rail 18. The first side rail 16 connects the frontcross member 12 with the rear cross member 14 at a first side of themotor vehicle sub-frame 10 while the second side rail 18 connects thefront cross member with the rear cross member at a second side of themotor vehicle sub-frame.

The front cross member 12, has a shape of an irregular box with no sidewalls. The rear cross member 14 is also an irregular box with no sidewall. As should be appreciated, the front cross member 12, the rearcross member 14 and the first and second side rails 16, 18 may all bemade via extrusions of aluminum or aluminum alloy.

Reference is now made to FIGS. 2A-2D illustrating the construction ofthe two side rails 16, 18. More specifically, each side rail 16, 18includes a first component 20. More specifically, the first component 20illustrated in FIG. 2A includes a first part 24 and a second part 26. Afirst end 28 of the first part 24 is joined to a second end 30 of thesecond part 26 so that the two parts are welded end to end and the twoparts have an extrusion axis extending parallel to the extrusion axisline 22.

As illustrated in FIGS. 2B and 2C each side rail 16, 18 also includes asecond component 32 having a second extrusion axis 34. The first element36 of the second component 32 is illustrated in FIG. 2B while the secondelement 38 of the second component is illustrated in FIG. 2C.

Each side rail 16, 18 is constructed from the first and second component20, 32. More specifically, the first component 20 includes a first wall40 forming an upper wall of the side rail 16, 18 and a second wall 42forming a lower wall of the side rail. The second component 32 includesa third wall 44 that forms an inner side wall of the side rail 16, 18and a fourth wall 46 that forms an outer sidewall of the side rail.

As best illustrated in FIG. 2D, the first element 36 is positionedinside the first part 24 while the second element 38 is positionedinside the second part 26. The third and fourth walls 44, 46 are thenjoined to the inner surfaces of the first and second walls 40, 42 bymeans of welding thereby providing at least partially closed side rails16, 18 as best illustrated in detail in FIG. 2D. In one particularlyuseful embodiment of the motor vehicle sub-frame 10, the walls 40, 46 ofthe components 20, 32 are welded together by one or more friction stirwelds. As best illustrated in FIG. 1, the first extrusion axis 22 of thefirst component 20 runs laterally while the second extrusion axis 34 ofthe second component 32 runs vertically in the assembled sub-frame 10.The two extrusion axes 22, 34 may form an included angle of between 60°and 90° or of between 70° and 90° or of between 80° and 90°. In theillustrated embodiment, the two extrusion axes 22, 34 are substantiallyperpendicular to one another.

Reference is now made to FIGS. 3 and 4 illustrating in detail the rearcross member 14 of the sub-frame 10. As illustrated, the rear crossmember 14 includes an extruded hollow body 48 having an extrusion axis50 that extends laterally across the sub-frame 10. A series of walls 52are positioned inside the hollow body 48 and extend across the hollowbody. Each wall 52 includes a first edge 54 and a second, opposite edge56 that are joined to the inner surface of the hollow body 48 byappropriate welds. In the illustrated embodiment, each wall 52 has alongitudinal axis that extends parallel to the extrusion axis 50 of thehollow body 48. Further each wall 52 is planar.

As further illustrated in FIGS. 3 and 4, the hollow body 48 includesvarious attachment points in the form of attachment holes 58 for, forexample, rear body attachments, stabilizer bar attachments, lowercontrol arm attachments and steering attachments. A cylindricalreinforcement 60 may be provided in the hollow body 48 to reinforce thehollow body around each attachment hole 58. As illustrated, a wall 52may extend radially outwardly from each cylindrical reinforcement 60.Here it should be appreciated that the walls 52 are not continuous butextend up to and are welded to the cylindrical reinforcements 60, theydo not cross the attachment hole 58 defined within the cylindricalreinforcements.

In summary, the sub-frame 10 provides a number of benefits andadvantages. The sub-frame 10 provides a desired strength relying uponfriction stir welds to assemble the components 20, 32 of the side rails16, 18 together, the rear cross member components 48, 52, 60 togetherand to join the side rails, 16, 18 to the rear cross member components.In contrast, one or more MIG welds are utilized to join the front crossmember 12 with the side rails 16, 18 through a first front bodyattachment 62 and second front body attachment 64 (see FIG. 1).

Further, the sub-frame 10 provides the desired bending and torsionresistances through the provision of side rails 16, 18 incorporating afirst component 20 having a first extrusion axis 22 and a secondcomponent 32 having a second extrusion axis 34 joined together so thatthe two extrusion axes form an included angle of between 60 and 90degrees. In one particularly useful embodiment, the two extrusion axes22, 34 are substantially perpendicular to one another and provide an atleast partially closed side rail.

The foregoing has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theembodiments to the precise form disclosed. Obvious modifications andvariations are possible in light of the above teachings. All suchmodifications and variations are within the scope of the appended claimswhen interpreted in accordance with the breadth to which they arefairly, legally and equitably entitled.

What is claimed:
 1. A cross member for a motor vehicle sub-frame,comprising: a hollow body having an extrusion axis; and a wall having afirst edge and a second edge, said wall being positioned inside andextending across said hollow body with said first edge and said secondedge joined to said hollow body.
 2. The cross member of claim 1, whereinsaid wall has a longitudinal axis that extends parallel to saidextrusion axis.
 3. The cross member of claim 2, wherein said wall isplanar.
 4. The cross member of claim 3, wherein said hollow bodyincludes an attachment point and said wall is aligned with saidattachment point.
 5. The cross member of claim 4, further including acylindrical reinforcement in said hollow body around said attachmentpoint.
 6. The cross member of claim 5, wherein said wall extendsradially outwardly from said cylindrical reinforcement but does notcross said attachment point defined within said cylindricalreinforcement.
 7. The cross member of claim 1, wherein said wall isplanar.
 8. The cross member of claim 7, wherein said hollow bodyincludes an attachment point and said wall is aligned with saidattachment point.
 9. The cross member of claim 8, further including acylindrical reinforcement in said hollow body around said attachmentpoint.
 10. The cross member of claim 9, wherein said wall extendsradially outwardly from said cylindrical reinforcement but does notcross said attachment point defined within said cylindricalreinforcement.
 11. The cross member of claim 1, wherein said hollow bodyincludes an attachment point and said wall is aligned with saidattachment point.
 12. The cross member of claim 11, further including acylindrical reinforcement in said hollow body around said attachmentpoint.
 13. The cross member of claim 12, wherein said wall extendsradially outwardly from said cylindrical reinforcement but does notcross said attachment point defined within said cylindricalreinforcement.